Ameloblastoma overview

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Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Ameloblastoma from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

Diagnostic Study of Choice

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

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CT

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Treatment

Medical Therapy

Surgery

Primary Prevention

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]

Overview

Ameloblastoma is a rare, benign tumor of odontogenic epithelium much more commonly appearing in the mandible than the maxilla. While these tumors are rarely malignant or metastatic (that is, they rarely spread to other parts of the body), and progress slowly, the resulting lesions can cause severe abnormalities of the face and jaw. Odontogenic tumors comprise of a complex group of lesions of diverse histopathological types and clinical behavior. Of all swellings of the oral cavity, 9% are odontogenic tumors and within this group, ameloblastoma accounts for 1% of lesions. WHO defines it as a locally invasive polymorphic neoplasia that often has a follicular or plexiform pattern in a fibrous stroma. Its behavior has been described as being benign but locally aggressive. In 20% of all cases the tumor can be found in the `maxilla, predominantly in the canine or molar region. Within the mandible, 70% are located in the molar region or the ascending ramus, 20% in the premolar region and 10% in the anterior part. Ameloblastoma was first described in 1868 by Broca. Based on the location, ameloblastoma may be classified into either intra-osseous or extra-osseous. Based on the clinicoradiologic features, ameloblastoma may be classified into four groups: solid or multicystic, unicystic, peripheral, and malignant. On gross pathology, the characteristic findings of ameloblastoma may include solid and cystic, mulitcystic and intraosseous or extraosseous, or rarely unicystic. On microscopic histopathological analysis, stellate reticulum, giant cells, subepithelial hyalinization, and columnar basal cells in palisading arrangement with vacuolated cytoplasm are characteristic findings of ameloblastoma. The exact pathophysiology of ameloblastoma is not fully understood. It is thought that ameloblastoma is the result of either suppression of matrix metalloproteinase-2 that may inhibit the local invasiveness of ameloblastoma, or there is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastomas. Genes involved in the pathogenesis of ameloblastoma include BRAF V600E. There are no established causes for ameloblastoma. It is thought that ameloblastoma is the result of either suppression of matrix metalloproteinase-2 that may inhibit the local invasiveness of ameloblastoma, or there is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastomas. Genes involved in the pathogenesis of ameloblastoma include BRAF V600E. The incidence of ameloblastoma is approximately 1.96, 1.20, 0.18, and 0.44 per 100,000 for black males, black females, white males, and white females respectively worldwide. Ameloblastoma affects men and women equally. There is no racial predilection to the ameloblastoma. Ameloblastoma usually occur in middle age group i.e. 20-40 years: the median age at diagnosis is 39 years. The incidence of ameloblastoma is approximately 1.96, 1.20, 0.18, and 0.44 per 100,000 for black males, black females, white males, and white females respectively worldwide. Ameloblastoma affects men and women equally. There is no racial predilection to the ameloblastoma. Ameloblastoma usually occur in middle age group i.e. 20-40 years: the median age at diagnosis is 39 years. Symptoms of ameloblastoma include mouth sores, painless swelling, loose teeth, facial deformity, swelling and numbness of the jaw, pain surrounding the teeth or jaw, and pain associated with the tissue growth, if ameloblastoma spreads to the sinus cavities and floor of the nose. The mainstay of therapy for ameloblastoma is surgery. Adjunctive chemotherapy/radiation/chemoradiation may be required.

Historical Perspective

Ameloblastoma was first described in 1868 by Broca.

Classification

Based on the location, ameloblastoma may be classified into either intra-osseous or extra-osseous. Based on the clinicoradiologic features, ameloblastoma may be classified into four groups: solid or multicystic, unicystic, peripheral, and malignant.

Pathophysiology

On gross pathology, the characteristic findings of ameloblastoma may include solid and cystic, mulitcystic and intraosseous or extraosseous, or rarely unicystic. On microscopic histopathological analysis, stellate reticulum, giant cells, subepithelial hyalinization, and columnar basal cells in palisading arrangement with vacuolated cytoplasm are characteristic findings of ameloblastoma. The exact pathophysiology of ameloblastoma is not fully understood. It is thought that ameloblastoma is the result of either suppression of matrix metalloproteinase-2 that may inhibit the local invasiveness of ameloblastoma, or there is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastomas. Genes involved in the pathogenesis of ameloblastoma include BRAF V600E.[1][2]

Causes

There are no established causes for ameloblastoma. It is thought that ameloblastoma is the result of either suppression of matrix metalloproteinase-2 that may inhibit the local invasiveness of ameloblastoma, or there is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastomas. Genes involved in the pathogenesis of ameloblastoma include BRAF V600E.

Differential Diagnosis

Ameloblastoma must be differentiated from other diseases that cause symptoms similar to those of ameloblastoma, such as dentigerous cyst, odontogenic keratocyst, odontogenic myxoma, aneurysmal bone cyst, fibrous dysplasia, hard odontoma, osteosaarcoma, and globulomaxillary cysts.

Epidemiology and Demographics

The incidence of ameloblastoma is approximately 1.96, 1.20, 0.18, and 0.44 per 100,000 for black males, black females, white males, and white females respectively worldwide. Ameloblastoma affects men and women equally. There is no racial predilection to the ameloblastoma. Ameloblastoma usually occur in middle age group i.e. 20-40 years: the median age at diagnosis is 39 years.

Risk Factors

There are no established risk factors for ameloblastoma. It is thought that common risk factors in the development of ameloblastoma may be dentigerous cyst, impacted teeth, injury to the mouth or jaw, infections of the teeth or gums, inflammation of the teeth or gums, infections by viruses, and lack of protein or minerals in the persons diet, and Gorlin-Goltz syndrome.

Screening

According to the United States Preventive Services Task Force, screening for ameloblastoma is not recommended.[3]

Natural History, Complications and Prognosis

History and Symptoms

Symptoms of ameloblastoma include mouth sores, painless swelling, loose teeth, facial deformity, swelling and numbness of the jaw, pain surrounding the teeth or jaw, and pain associated with the tissue growth, if ameloblastoma spreads to the sinus cavities and floor of the nose.

Physical Examination

Laboratory Findings

There are no diagnostic lab findings associated with ameloblastoma.

Head X Ray

On head x ray, ameloblastoma is characterized by polycystic, honeycombed mass arising within the alveolar border of the jaw.

CT

On head and neck CT, ameloblastoma is characterized by multiloculated, expansile "soap-bubble" lesion, with well demarcated borders, no matrix calcification, and occasionally erosion of the adjacent tooth roots.

MRI

Head and neck MRI scan may be diagnostic of ameloblastoma. Findings on MRI suggestive of ameloblastoma include mixed solid and cystic pattern, with thick irregular wall, often with papillary solid structures projecting into the lesion.

Other Imaging Findings

There are no other imaging findings findings associated with acoustic neuroma.

Other Diagnostic Studies

Other diagnostic studies for ameloblastoma include incisional biopsy. Incisional biopsy is diagnostic of ameloblastoma.

Medical Therapy

The mainstay of therapy for ameloblastoma is surgery. Adjunctive chemotherapy/radiation/chemoradiation may be required.

Surgery

The mainstay of therapy for ameloblastoma is surgery. The predominant therapy for ameloblastoma is surgical resection. Adjunctive chemotherapy/radiation/chemoradiation may be required.

Primary Prevention

There are no primary preventive measures available for ameloblastoma.

Secondary Prevention

Secondary prevention strategies following ameloblastoma include follow-up examination at regular intervals for at least 10 years.

References

  1. Ameloblastoma. Wikipedia(2015) https://en.wikipedia.org/wiki/Ameloblastoma Accessed on December 25, 2015
  2. Ameloblastoma. Libre pathology(2015) http://librepathology.org/wiki/index.php/Ameloblastoma Accessed on December 25, 2015
  3. http://www.uspreventiveservicestaskforce.org/BrowseRec/Search?s=ameloblastoma Accessed on December 28, 2015.

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